Instrument for transmitting vocal sounds



(No Model.)

G. J. STUART.

INSTRUMENT FOR TRANSMITTING VOGAL SOUNDS.

No. 341,519. Patented May 11, 1886.

3m akin N. PETERS. Phemunia'gh nen Washington. 04 c.

UNITED STATES PATENT OFFI E.

CHARLES J. STUART, 0F LOIVELL, MASSACHUSETTS.

INSTRUMENT FOR TRANSMITTING VOCAL SOUNDS.

SPECIFICATION forming part of Letters Patent No. 341N519, dated May 11,1886.

Application filed July 16, 1585.

My invention relates to transmitters for transmitting vocal sounds overawire or cord either operating electrically or mechanically; and itconsists in certain additions to and improvements in the arrangement oftransmitters. substantially ashereinafter described and claimed.

In tl1edrawings,Figure1 is asectional view of a portion of a telephonictransmitter provided with my improvements. Fig. 2 is an enlarged view ofthe improved mouthpiece detached, partly in section, showing the same.Fig. 3 is a front end view of the same.

A is the transmitter, of ordinary construction, containing the metallicdiaphragm B, having a carbon contact-piece, 6, attached to its center. Aspring, 8, is attached to the wooden casing of the transmitter, and hason its free end another carbon contact-piece, s, which is pressed by thespring against the contact-piece b, in the ordinary manner. L is theline-wire, which is connected on one side to the diaphragm B, and on theother to the spring 8. The transmitter has an aperture, 0, through thecasing in front of the diaphragm, to permit speaking against the latter.All of these parts are well known and understood, and I do not intend toconfine myinvention to any particular form of transmitter, as itisapplicable to any one having the diaphragm B and the opening 0 oppositethe diaphragm.

My invention consists in placing opposite to the diaphragm B, on thefront side, against which the air-vibrations set in motion by the voicestrike, a body of non-resonant substance in such a position as tocompress such airvibrations between it and the diaphragm, and cause themto act more forcibly upon the latter, without creating conflicting airvibrations from such substance which will break up or destroy thosecreated by the voice.

The non-resonant substance which I have found to give the best effectsfor the purpose Serial No. 171,753. (No model.)

described is air, and I confine a column or body of it opposite thediaphragm B of the transmitter, in such a manner as to prevent itsescape at the instant that the air-waves of the voice enter the aperture0, and pass between such column or body and the diaphragm, and thusconfine the waves between such column or body and the diaphragm, andcause them to exert greater force upon the latter without creatingsupplemental or reflex waves, which would break up the vibrations of thediaphragm in response to the airwaves of the voice. By this. means I amenabled to increase the power of the transmitter to convey to theliuewire L the proper vibrations to reproduce speech at another stationon the line, and at the same time I avoid all unpleasant ringing orbreaks in the reproduced sounds.

In carrying out my invention I provide a supplemental mouthpiece, M,funnel-shaped, and having its smaller end snugly fitted into thecircular aperture 0. IVit-hin the inner and smaller end of thismouth-piece I fix, by four small bars or struts, m m, the conicalreservoir N, with its larger or open end to ward the diaphragm and ashort distance from it, so as to leave spaces around its outer edge forthe airwaves of the voice to pass between it and the mouth-piece M andimpinge against the diaphragm B. \Vhen the air-reservoir N is madeofsufiicient internal depth to confine a column of air of a certainlength within it, with the exposed end of the column toward diaphragm B,as shown, it will be found that no vibrations of the reservoir N willtake place which will set in motion airwaves that will affect diaphragmB, and the transmitter will convey only the vibrations of the airwavesof the voice, greatly amplified by being forced into the space betweenthe column of air cpnfined in reservoirN and the diaphragm.

I have shown the reservoir N of a conical shape, in order to allow theair-waves of the voice to pass by its exterior freely and enter the\aperture 0, around andbetween it and mouth-piece M; but it is notnecessary that the reservoir should be made of this form to produce goodresults, as I have produced such resultswith it made in the form of ahollow cube and of a hollow pyramid and of ahollow hemisphere secured inthe mouth-piece M, with the open sidein the same position as reservoirN, it only being essential in each case that the column of air in thedirection of the axis of reservoir N, confined within either of thesedifferent forms of reservoir, shall be of a certain length and Withincertain limits. Thelonger it is the more the power of the transmitterwill be amplified'and the clearer it will transmit speech to anotherstation on the line. Thusl have found a length of air-column of one-halfinch confined in the reservoir N to increase the power of thetransmitter one-half, and a length of three-fourths of an inch to nearlydouble its power, and a length of about one inch to nearly triple itspower in long-distance telephony.

It will be observed that my improvement is portable, and can be appliedto any transmitter at will.

Instead of a column of air, cork or some other non-resonant substancemay be employed in substantially the same form and position as the bodyof air confined in reservoir N, and it will give good results; but Iprefer to employ the confined air as described.

What I claim as new and of my invention 1S- 1. In a telephonictransmitter having aperture O and diaphragm B, a mass or column ofnon-resonant substance placed opposite the diaphragm and at a distancetherefrom in the aperture 0, and in the path of the voice-waves enteringthe transmitter, and presenting a flat surface to said diaphragm,substantially as described. p

2. The combination, with the transmitter having the aperture 0 anddiaphragm B, ofthe mouth-piece M and its air-reservoir N, formed with asound passage or passages between said mouth-piece and said reservoir,and having the open and unobstructed end of the latter toward thediaphragm, substantially as described. v

3. In combination with the sound-receiver of the telephone-transmitter,the sound-deflector, preferably conical or conoidal in exterior form,located inside of the sound-receiver, with its apex presented toward thespeaker, and arranged to form an annular space between its base and thewalls of the sound-receiver, substantially as described.

CHAS. J. STUART.

\Vitnesses:

JOHN D. REED, GEORGE WV. POORE.

